A conventional multispectral imaging system includes: 1) optical elements (e.g., mirrors, lenses, etc.) that are configured to manipulate and direct light; 2) filters that are configured to filter particular wavelengths of light; 3) detectors that are configured to generate signals that are indicative of amplitudes of light at the particular wavelengths; and 4) processing circuitry that is configured to generate meaningful output based upon the signals generated by the detectors. The optical elements, filters, and detectors are selected and arranged relative to one another to allow for analysis of wavelengths over multiple spectrums of light, ranging from the visible spectrum (as low as ˜400 nanometers) up to long wave infrared (up to as high as ˜12 micrometers).
In an example, a conventional multispectral imaging system can be gimbaled, thereby allowing for alteration of a field of view of such an imaging system. A conventional gimbaled multispectral imaging system, however, tends to be relatively expensive to design and build. Further, a design of a conventional gimbaled multispectral imaging system is typically only well-suited for a small set of wavelengths of light, aperture sizes, detector configurations, and processing configurations. That is, the design is not readily extendible; if it is desirable to analyze other ranges of wavelengths, other aperture sizes, other detector configurations, or other processing configurations, then an entirely new design is typically generated. Moreover, depending on the application, performance of a gimbaled multispectral imaging system can be limited by the weight and size of the system.
To reduce the size and weight of a multispectral imaging system, single-aperture (e.g., primary mirror) designs have been proposed, where the multispectral imaging system includes beam splitters in optical communication with the primary mirror, and respective detectors in optical communication with the beam splitters. The primary mirror is configured to form a light bundle, and the beam splitters progressively split the light bundle by wavelength (e.g., such that each beam splitter directs a respective wavelength of interest to a respective detector).
The single aperture and beam splitter approach described above leads to several complications: 1) a potential need for different focal lengths for various optical wavelengths with a single front end optical design; 2) a longer beam path may be needed to have room to split the light bundle and change focal lengths, which often requires a re-imaging system, which reduces performance; 3) optically efficient beam splitters with sharp transitions between transmission and reflection are required; 4) the potential need for many optical elements which both increases complexity and cost but also reduces performance in the form of reduced transmission and/or increased self-emission; and 5) very tight alignment tolerances are needed, especially for the visible elements (to maintain performance).